Screw and method of making same



JimZ, 13%.. D. E. JOHNSON 2,152,891

SCREW AND METHOD OF MAKING SAME Filed Feb. 18, 1938 3 Sheets-Sheet l G Y'm Dav/'0 Ha /ms n june2,1939 DUEL-JOHNSON mfiwm SCREW AND METHOD OFMAKING SAMEv Filed Feb. 18 1938 3 Sheets-Sheet 2 h w A W Y 11 v if W ilkJune 20, 1939. D. idol-mow 1 m i Feb 18, 1958 sfsneets-sheey s &

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Patented June 20, 1939 UNITED STATES PATENT OFFICE 2,162,891. SCREW ANDMn'rnon or MAKING SAME David E. Johnson, Rockford, Ill.

Application February 18, 1938, Serial No. 191,151- "12 Claims. (oi.Iii-l) My invention relates to screws and blanks therefor, and moreparticularly to blanks for gimlet points screws, as well as to a methodfor manufacturing the same.

6 Wood and so-called sheet metal screws are provided with a tapered orgimlet point having a thread thereon, the pitch diameter of whichdecreases progressively to the screw tip. In making such screws, it hasheretofore been proposed to forge a head on one end of a blank, toremove metal from the other end to form a conical point, and then toroll the threads thereon. When such operations are carried. out inseparate machines,

. the process of manufacture is comparatively slow because of thenecessary handling of the blanks between operations. Although automaticcombined blank forming and threading machines, such as that shown in thepatent to Earl R. Frost, No. 2,020,658, have heretofore beensuccessfully used to form blanks in large quantities for various typesof screws and bolts and to threadthe same, all in the same machine, ithasnot been possible to use such a machine efliciently in making gimlepoint screws. This is because the amount of 5 metal which mustbe'removed in orderto form a point of the required shape iscomparatively large and, as a consequence, thev operation requires so-much time for each blank that the speed of the heading, trimming andthreading mechanisms.

must be reduced substantially below their normal operating speeds inorder to maintain the proper timed relation between the variousoperations which are sequentially performed. In addition, the cuttingtool used for pointing becomes dulled 5 requiring frequent shut-down ofthe machine for replacement thereof. It will thusbe seen that theoperation of a machine ofthis 'type is very slow and inefllcient whenused for making gimlet point screws as compared to what may be termedits normal operation in making bolts, ma-

chine screws, cap screws and the like.

One object of 'the present invention is to provide a novel method ofpointing screw blanks gimlet point threads may be rolled. v

Another object is to provide for forging the point on one end of thescrew blank while the head forming operations are being performed on theother end.

A further object of my invention is to provide a gimlet point screwblank having a. point'of new and improved construction.

Further objects and advantages of my invention .will become apparent asthe following de- 5 scription proceeds and the features of novelty.which characterize my invention, are pointed out with particularity inthe-claims annexed to and forming a part of this specification.

For a better understanding of my invention; 10 reference may be had tothe accompanying drawings, in which:

Figure 1 is a top plan view of a unitary screw blank forming andthreading machlne'for carryr ing out my invention.

Fig. 2 is an enlarged elevational view partly in section taken along theline 2-2 of Fig. 1 showing the blankv supporting dies and the cut-oi!and transfer mechanisms.

Fig. 3 is an enlarged sectional view alongthe 20 line 3-3 of Fig. 2.

Fig. 4 is a detail view partly in section of the mechanism used fortransferring blanks from the forming dies to the roll threading dies.

Fig. 5 is an enlarged sectional view" along the 86 line 55 in Fig. '4. 4

Fig. .6 is a cross-sectional view of the roll. threading diesillustrating the manner of finishing a gimlet point screw.

Fig. 7 is an enlarged sectional view similar to Fig. 3 and illustratinga modified form of die, mechanism. In accordance with my improvedmethod, blanks for gimlet point screws are made from lengths of wirestock preferablyhaving a diameter substantially equal to the bodyportion or {stem of the finished screws. As herein illustrated, theimproved method of pointing the blanks preparatory to rolling a gimletpoint thread thereon comprises forcing one end portion of the blank 40int'oza die recess shaped to forma short protrusion of reducedcross-section on the end of the blank. Then this reduced end portion isfurther reduced in diameter by forcing ltinto a second and smallerdrawing die. A generally tapered end or "point" 45 is thus formed whichso closely simulates the shape of the conical point ordinarily used thata perfect gimlet point thread -of progressively decreasing diameter maybe formed on the blank ina roll" threading operation.- The drawing op-60 erations by which the blank is pointed are preferably carried outsimultaneously with the forg- 1 ing operations in which the opposite endof the length of stock is upset and shaped by suitable dies to form ascrew head.

In the drawings, the invention is illustrated in conjunction with acombined heading, trimming and roll threading machine similar in itsgeneral construction and arrangement of parts to that shown in PatentNo. 2,020,658 to'which reference may be had for details of constructionand operation. My machine differs in oneimportant respect from the oneshown in this patent, however, in that the screw blanks are pointed byforging of the metal comprising one end of the blanks rather than by ametal removing operation as is the case in the machine shown in saidpatent. As a consequence, my machine may be operated with great rapidityand emciency to form blanks for gimlet point screws.

Referring first to Fig. l, the combined heading and threading machinethere shown includes a bed frame it of heavy and rigid constructionusual manner as a U-shaped die breast ii.

having one end of. its upper side formed inthe A. header slide or ram i2is mounted in horizontal guideways to reciprocate longitudinally of theframe toward and away from the die breast H. The header l2 may bereciprocated by a suitable driving mechanism (not shown) housed in thesupporting frame it). In the particular machine illustrated, three setsof blank supporting" dies l3, l4 and I5 and cooperating punches i6, Handl8, carried by the die breast H and header l2, respectively, operatesuccessively on lengths of wire stock supported in the dies. The headedand pointed blanks are carried by a transfer mechanism to a pair ofreciprocating roll threading dies, hereinafter described, which form Ithreads on the blanks.

A wire I9 is fed from a reel or other source of supply into the machineby any suitable type of feeding mechanism. As the stock is fed throughthe bed frame l0, it engages an adjustable abutment 2i. A cut-ofl arm 22is arranged to engage the stock, shear off blanks of desired length andcarry the same into alinement with the first die IS. The arm 22 ispivoted at 23 (Fig. 2) on the frame If! and is operated by a cam 24engaging a roller 25 carried by a lateral extension on the arm 22. Thecam 24 is on a cam shaft 26 which is, in turn, driven in timed relationwith the reciprocations of the header slide l2. During each cycle ofoperation of the machine; the arm 22 is rocked by the cam 24 to shearoff a blank and carry the same into alinement with the die l3 during thetime the header slide I2 is retracted and then to return to its initialposition to receive another blank while the header slide is movedforward into engagement with thework. The cut-off mechanism may be ofthe well known type disclosed in the patent to William L. Clouse No.1,856,028, issued April 26, 1932, and consequently need not be describedhere in further detail.

Upon reference to Fig. 3, it will be seen that the die I3 is providedwith a bore 21 communieating with the face of the die, which issubstantially equal in length to the body portion proper areaeor thebore 21 so that one end of the stock is forced axially through thethroat 29 and into the .bore Bil to extrude a protrusion of reducedcross-section on the end of the blank in the form of a cylindrical endportion 30 of reduced diameter terminating in a beveled face or section29 At the same time, the other end of the length of stock isupset andgiven a substantially frustoconical shape as shown in Fig.3.

The second die M is also provided with a longitudinal bore 32 ofsubstantially the same dimensions as the bore 21 in the die It andterminating indicated at 37', in order to slightly enlarge the diameterof the stem of the'screw at the base of its head. The punch ll,which'cooperates with the die it, is provided with a spherical recess ordie cavity 38 which serves to shape the upset end of the length ofstock. It will thus be seen that when a blank is transferredufrom thedie it to the die M, the punch II will force the same into the bore 32so that the reduced end portion 30* thereof is moved axially for a partof its length through the throat 34 to form the reducedend portion 36and beveled section 35 between the portions 36 and 36. In the sameoperation, the upset end is forged by the punch H to give, the desiredshape to the head 38 A plurality of relatively short stepped portions ofsuccessively smaller diameter than the'body portion of the stock arethus formed on one end of the blank' giving the same a generally pointedcontour and a fiat end as is required. The relative lengths of thecylindrical portions 35 and 36 are such that ends of these portions andthe end of the stem 28 proper constitute elements of a cone of the shapedesired for producing the desired taper on the finished screw when thelatwr is roll threaded.

The die I5 is simply a holding die which maintains the blank in positionto be operated upon by the punch II, which in the machine illustratedconstitutes a trimming die. A longitudinally extending bore 39 is formedin the punch l8 and a series of inwardly extending cutting teeth 40 areprovided at the outer end of this'bore. These teeth serve to cutserrations 4| on the periphery of the head of the screw blank. Theseserra-- .tions, which serve the same general purpose as the. slot formedin ordinary wood screws, may be engaged by a suitable socket headeddriving tool whenthe finished screws are used. Of course, any otherdesired type of head may be formed.

The lengths of stock severed from the wire I! are moved successivelyfrom the die It! tothe die l4 and then from the die H to the die '5 bytransfer mechanism operating in timed sequence with the movement of theheader slide l2. As shown in Fig. 2, this transfer mechanism includes. aplate 42 which is slidably mounted in horizontal guides 43. The latterare, irr-turn, mounted on a slide 44' (Fig. 1) which is adapted toreciprocate vertically along guides 44. --A horizontally disposed hollowbracket 45 supports the vertical guides 44. 5

Vertical reciprocatory movement is impartedta ment with the nextsuccessive dies.

suitable driving connection the rock shaft 41 is oscillated by a cam 41(Fig. 2) in timed relation with respect to the header slide I2.Horizontal reciprocatory movement of the plate 42 with re spect to thehorizontal guides 45 is imparted thereto by a link 48 pivotallyconnected at its opposite ends to the oscillating arm 22 and to theplate 42. v

The plate "is provided with two pairs of gers adapted to engagesuccessive screw blanks upon downward movement of the plate 42. Thenupon the horizontal movement of the plate. 42 these fingers carry thescrew blanks into aline-' In the particular arrangement shown in Fig. 2,a pair of depending arms 49 and 50 are fast on the plate (Ill 4i.- Thearm 49 is arranged so that its inner face is flush with the opening inthe die I3 when the arm 22-is at one end of its stroke, and flush with.the opening in the die I4 when the arm is at the other end of itsstroke. The arm 58 is similarly arranged with respect to the openings inthe dies I4 and I5.

A pair of pivoted arms 5I and 52 cooperate-with the arms 49 and 50respectively. Each arm 5| and 52 carries at its lower end a hardenedwear plate 53 having a recess adapted to receive and hold a screw blank.Each of the arms 5I and 52 is secured by set screws to an eccentric on astud rotatably mounted in the plate 42 so that the set screws may beloosened and the stud rotated to adjust the vertical position of the armand aline the holding recess with the adjacent die openings. Anadjustable spring tension member 54 normally holds each arm 5I and 52pressed' spect to the movement of the transfer mechanism by a suitabledriving arrangement to move the blanks out of the dies into a positionto be grasped by the fingers of the transfer mechanism.

It will thus be seen that in the operation of the machine described,successive lengths of stock severed from the wire I9 are movedprogressively to the dies I3, I4 and I5. These dies and theircooperating punches successively shape or forge the lengths of stockuntil a finished blank, such as the blank 55 shown in Fig. 3 is formed.This blank has a suitably shaped and trimmed head and a stepped end orpoint adapted tohave a thread of decreasing pitch diameter rolledthereon. Thus, while the stepped point construe tion is not of trulyfrusto conical shape, it does header slide is retracted. Then, as thepunch I8 againmoves forwardly in the next cycle, the

reduced end of theblank 55 strikes against the head of the nextsuccessive blank presented to the opening in the die I5 by the transfermechanism so that the blank 55 will be advanced longitudinally along thebore 59 in the punch l8."

As shown' in Fig. 4, a tubular conduit 55 is mounted on the header slideI2 in communication with the rear end of' the bore 59 so as toreceive'the finished blanks 55 from the latter. The tube 55-curvesupwardly to elevate the blanks and has a downwardly extending portionformed in its lower side with a slot 51 which permits the stems of thefinished blanks to pass therethrough while the heads are retained in thetube. Thus, the stems of the blank hang downwardly (Figs.

land 5). x

Before the blanks are discharged from the tube, their stems pass betweeninclined guide rails 58 and 59 (Fig. 5) which, in the present instance,are slidably and pivotally connected to the tube 55 by a yoke. 58'thereby allowing for independent reciprocation of the header slide.The, blanks slide down along the rails 58 and 59 and are delivered to apair of reciprocating roll threading well understood in the art.

I The die BI is secured to the, rear end portion of the reciprocatingheader slide l2 by a suitable die holder 53 and is thus reciprocatedbyflmovement of the header slide. The cooperating roll threading die 52is mounted for horizontal'reciprocatory movement on the base frame-IIIby a suitable die holder 52 and guiding arrangement.' Movement isimparted thereto by a linkage mechanism including a walking beam 54pivotally mounted on the supporting frame Ill and pivotallyconnected atits opposite ends to the header slide l2 and tothe die holder 52 bylinks 55 and. 55 respectively.

Beyond the end of the rail 58, the rail 59 is'provided with a lateralextension 51 forming an abutment-at the end of the track. The rail 58terminates short of the extension 51 thus leaving a passage therebetweenof the same size as the passage between the rails 58 and 59. A pair oftrack members 58 are'mounted on theholder 52 of the roll threading die52 and register with the ends of the rails 58 and 59 when the die 52 vis at one extremity of its path of movement.

,for retracting the bell crank lever II upon disengagement thereof bythe die support 52".

A bell crank lever I2 is arranged to force the screw blanks 55 out ofposition between the members 58 and into position between the. rollthreading dies 5| and 52 when the holder 52" reaches the end of itsrearward movement. This lever I2 is pivoted on the die holder 52 and hasa hooked end I3 riding over the top of the mem-' bers 58 to engagethehead of a screw blank 55 positioned between the latter. The opposite endof the bell crank lever I2 is provided with a roller I4 riding on aperipheral cam I5 rigidly secured w the base frame III. The lever I2 isspring biased into engagement with the cam I5 so that, as the holder 52moves, rearwardly, the bell crank lever I2 is rocked in acounterclockwise direction as viewed in Fig: .1, bringing the hookedpositioned between the member 68. As the holder 62 reaches the end ofits rearward movement, the contour of the cam'l5 allows the end I3 ofthe 1 bell crank lever to force the blank out from between the membersI58 and into position between shaped to form a gimlet point thread 88(Fig. 6) v of decreasing pitch diameter on the reduced end portion ofthe blank, which is a continuation of the thread 8| also formed by theroll threading dies on the stem or body portion 82 of the blank. Afinished gimlet point screw, such as that shown in Fig; 6, is thusproduced. The finished screws are ejected from between the dies 5i and62 upon the termination of their roll threading movement into an openingI5 (Fig. l) in the base frame Ill, whichpommunicates with a receptaclein which they are received. An oscillating finger-"TI, pivotaily mountedon the holder 62, is normally held out of contact with the blanksbetween the diesGI and 62 and a stop pin is arranged to engage thefinger TI to move it into position to eject the finished screwsfrombetween the dies upon the completion of their roll threadingmovement. The details of construction and operation of the rollthreading dies, and the operating mechanism, therefore need not bedescribed here in further detail since such dies and mechanism are wellknown in the art. The operating mechanism illustrated in substantiallythe same as that shown in Patent No. 2,020,658 previously referred to.

Instead of separating the frusto-conical or beveled portions Mi and'il5by the intervening, cylindrical step the latter step may, if desired, beeliminated entirely or substantially so that the two portions merge andform a single.

longer beveled portion indicated at I in Fig. 7

'in the double extruding operation above described. In such a case, theend step would be elongated somewhat as indicated at I 36 Forging of themetal stock into this modified shape may be accomplished by punches anddies of the form shown in Fig. 7. The three sets of dies and cooperatingpunches of Fig. 7 are intended for use in a machine like that of Figs. 1and 2 and accordingly corresponding parts have been designated in Fig. 7by reference numerals which are 100 greater than the reference nu-' tionserving to elongate the beveled face and the cylindrical portion; I

A longitudinal bore I21 in the die II 3 receives the blank I28 severedfrom the stock l9 and is of a diameter substantially equal to theinitial diin a bevel-faced throat I29, which merges with ameter of thestock. This bore I21 terminates asecond bore I30 of smaller'diameter orcross section. The horizontally. reciprocating punch sarcasm end I3 intoengagement with a. screw blank 5,5

IE6, which cooperates with the die H3, is provided with a frusto-conicalrecess or die cavity .I3I in the front face thereof. Consequently,

' when a length of stock is positioned between the punch IIS and dieII3, the punch forces the 5 length of stock into the bore I21 so thatone end of the stock is extruded through the throat I29 and into thebore I30 to form a cylindrical end portion I3Il of reduced diameter anda beveled section I29. At this point, the end of the blank is reduced toa shape similar to the shape produced by the die It previouslydescribed.

The blank forged by the punch and die II$-I I3 is ejected by a plunger3' and then transferred to the second die IId. This die cooperates witha punch Ill and is provided with a longitudinal bore I32 ofsubstantially the same dimensions as the bore I27 in the die IE3, andterminating in a bevel-faced throat I83. The throat I33 is substantiallylonger than the throat I29 and merges into a bore I36 which is also ofsubstantially smaller diameter than the bore I30. As the punch I IIadvances the blank into the die H6, the inner endof the blank isextruded into the throat I33 and at the same time the head is v shapedby a spherical die recess I38 in the face of the end of the blank by thedie H3, is elongated:

to form a frusto-conical extension of the previously formed beveled-faceI29, and a small cylindrical extension I36 Upon the completion of thissecond forging operation, the blank is ejected from the die by a plungerH4 The third die H5, like the die I5, is simply a holding die whichmaintains the blank in position to be operated upon by a c'ooperatingpunch H8, shown as a trimming die and identical in construction with thepunch I8 (Fig. 3). A longitudinally extending bore I39 formed in thepunch H8 receives the finished blanks I55 as they are ejected from thedie I I5 by a plunger H5 'Serrations MI onthe head of the blank are cutby die teeth I40 on the punchd I8 thereby trimming and finishing thehead of the blank. The serrations also serve to accommodate the screwhead for engagement by a cooperating v'al blank is struck by the plungerand forced through the trimming die, the inclined walls of the recess Iengage the squared edge of the portion I36 and bevelthe edge slightlyas' indicated at I46 (Fig. 7) thereby further reducing the end of theblank'to a shape simulating a true cone.

It will thus be seen that I have provided a,

method of forming gimlet point screws in which a suitably pointed blankis provided without the necessity of employing any metal removing op- Ierations and without wasting any metal and in which dishing of thereduced ends is avoided. In addition, my improved method may be carriedout with sufllcient rapidity and efficiency that the blanks may beheaded and completely formed in aminimum number of operations and with aminimum amountof handling. .The improved combined blank forming and rollthreading machine, which I have disclosed herein, is

entirely automatic in its operation and serves to produceaccuratelymachined and finished gimlet point screws from raw stockspeedily and emciently.

Although I have shown certain particular embodiments of my invention,which have been described in detail for purposes of illustration, 1 donot desire my invention to be limited to the particular constructionsshown and described, and

I intend in the appended-claims to cover all modifications andalternative methods or devices within the spirit and scope of myinvention.

The present application is a continuation in part, of my copendingapplication Serial No.

73,991 filed April 13, 1936.

Iclaim as my invention:

1. The method of making gimlet point screws which comprises upsettingone end ofa length oi stock to form the head portion of the same and inthe same operation extruding the other end portion to form the same in agenerally beveled shape,'shaping said upset head portion and in the sameoperation further extruding said other end portion to increase thelength oi the reduced section, and rolling a continuous thread on thestock extending from said other end thereof along the beveled portionand along at least a part of the intermediate portion or. the stock.

2. The method of making a gimlet point screw which comprisesprogressively reducing the cross section of a length of stock to agenerally tapered the same operation reducing the cross-section of '0!stock to form the head portion of the same.

the other end of the stock to form a short end portion of reducedcross-section and an elongated portion intermediate said head and endportion, and forming along both of said portions a continuous thread ofa pitch diameter which decreases along said end portion to define agimlet point thereon. 4

4. The method of forming a gimlet point screw which comprises upsettingone end of a length of wire stock to form a head and a cylindrical stem,drawing out a short length of the end'of said stem to iorma portion ofreduced cross-section corresponding in length to the length of thetapered portion of the gimlet point thread to be formed. and rolling agimlet point thread on said reduced portion and at leasta part of saidstem.

5.'The method of making gimlet point screws which comprises upsettingone end of-a length and in the same operation reducing the diameter ofthe other end portion of the stock to form a reduced end portionthereon, shaping saidupset head portion and in the same operationfurther reducing the diameter or said reduced end portion for a part ofits length, and forming'a continuousthread on the stock extending alongthe reduced end portions. I

' 6. The method of making gimlet point screws which comprises upsettingone end of a length of stock to form the head portion of the same and inthe same operation reducing the diameter of the other end portion 0! thestock to form a reduced end portion thereon, shaping said upsetheadportion and in the same operation further reducing the diameter ofsaid reduced end portion for a part-or lts length, and rolling acontinuous thread on the stock extending along the reduced portions andalong at least apart of the stock between the head and reduced portions.

7. The method 0! making gimlet point screws which comprises reducing thediameter of one end 01 a blank to form a reduced cylindrical end portionof smaller diameter than the body portion of the blank, reducing thediameter of said reduced end portion for a. part of its length to.

of smaller diameter than the first named end portion thereby giving theend of the blank a 7 generally pointed contour on which a gimlet pointthread may be rolled, and rolling a continuous thread from onereducedportion to another.

8. The method of making blanks for gimlet point screws'which comprisesthe successive head forming operations of upsetting one end of a lengthof stock and shaping a head from the upset end of the stock, andpointing the other end of the stock by forging said otherflend oi thestock simultaneously with said head forming operations to'form aplurality of relatively short stepped cylindrical portlons'oisuccessively smaller diameter than the body portion of the stock andbeveled portions between the adjacent cylindrical portions-oi giflerent.diameters.

form a second reduced cylindrical 'end portion 9. The method of making agimlet point screw 4 which comprises upsetting one end of a length ofstock to form the head portion of the same and in the same operationextrudingthe other end portion of the stock to form a protrusion thereonof reduced diameter joined to the body 0! the stock by a beveled-facedsection, shaping said upset head portion and in the same operationfurther extruding said other end portion to further reduce the diameterof said protrusion and lengthensaid beveled-face section, and rolling acontinuous thread on said stock extending from said other end thereofalong at least a part'of the adjacent portion of the stock.

10. As an article of manufacture, a gimlet point screw blank having a;cylindrical stem adapted to have threads rolled ,thereon, a head formedat one end of said stem, a plurality of relatively short steppedportions at the other second cylindrical portion -tu'rther reduced indiameter, and a second beveled surface between said cylindricalportions, the combined axial lengths of saidportions and said surfacesbeing approximately equal to the tapered portion of the gimlet thread tobe rolled on the blank.

12. As an article or manuiacture, a gimlet point screw blank having acylindrical stem and a pointed end comprising a short cylindrical por-'tion of reduced diameter joined to the stem by a section having abeveled surface, the actual length of said pointed end beingapproximately equal to the tapered portion of the gimlet thread to berolled thereon.

DAVID E. JOHNSON.

end of the stem having successively smaller di-

